Ventilating structure and mounting structure for electronic apparatus

ABSTRACT

Electronic apparatus is housed in a dual housing structure that includes an inner case housing electronics and an outer case surrounding the inner case. The inner and outer cases have respective intake openings, and in the area where the respective intake openings are provided, the inner and outer cases are spaced from each other by a sufficient distance such that an intake chamber is defined between the inner and outer cases. The intake opening of the inner case and the intake opening of the outer case are displaced from each other with respect to a front-and-rear direction of the apparatus so as to provide a nonlinear intake passage.

BACKGROUND OF THE INVENTION

The present invention relates to ventilating structures for use inelectronic apparatus such as video projectors. The present inventionalso relates to ventilating structures for use in video projectorshaving a projecting lens in their front end section. The presentinvention also relates to structures for mounting a ventilating fan unitfor use in electronic apparatus such as video projectors.

In homes and offices, video projectors are being popularly used forprojecting video images on a screen. Generally, each of the videoprojectors includes a built-in light source of great light quantity forprojecting video images on a large screen. For example, the light sourceis in the form of an incandescent lamp that consumes electric power inthe order of 150 watts. Electronic circuitry for processing videosignals in the video projector also consumes electric power more than 50watts and thus the video projector as a whole consumes power exceeding200 watts, so that a considerable amount of heat is generated in theinterior of the video projector. Because sufficient heat dissipation isnot attainable by natural ventilation, an electric fan is normally usedto compulsorily introduce external air into the interior of the videoprojector or discharge heated air from the interior, so as to cool theelectronics and lamp in the interior of the video projector.

However, because the video projector is used quite near the user orvideo viewer(s), the video viewer(s) would be significantly disturbed bygreat noise produced by the ventilation operations. Further, heated airdischarged from the interior of the video projector would greatlydisplease and disturb the video viewer(s). Therefore, it has beenconventional to support the fan unit at a plurality of corners thereofby means of supporting members each made of a rubber or other resilientmaterial, in order to absorb vibrations of the fan unit utilizing theresiliency of the supporting members. However, because characteristicsof the rubber supporting members tend to be greatly varied bytemperature changes, the resiliency of the supporting members would beweakened by the heated exhaust air so that the vibrations of the fanunit are undesirably transmitted to the outer case of the videoprojector. Further, with the fan unit thus supported at its corners,horizontal vibrations of the fan unit can not be sufficiently absorbed.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a ventilating structure for an electronic apparatus which canminimize noise caused by the ventilation operations and allows a user touse the electronic apparatus without being disturbed by the ventilationoperations.

It is another object of the present invention to provide a ventilatingstructure for a video projector which can reduce noise caused by theventilation operations and allows a user to use the video projectorwithout being disturbed by the ventilation operations.

It is still another object of the present invention to provide amounting structure for a fan unit which can minimize transmission, to anouter case, of horizontal vibrations of the fan unit and therebyeffectively reduce noise caused by the ventilation operations.

According to an aspect of the present invention, there is provided aventilating structure for an electronic apparatus, which comprises aninner case that houses electronics, and an outer case that houses theinner case along with the electronics. The inner case and the outer caseeach have an intake opening, and in the area where the respective intakeopenings are provided, the inner case and the outer case are spaced fromeach other by a sufficient distance such that an intake chamber isdefined between the inner case and the outer case.

In the ventilating structure, the intake opening of the inner case andthe intake opening of the outer case are displaced from each other withrespect to a front-and-rear direction of the electronic apparatus so asto provide a nonlinear intake passage in a rear end section of theelectronic apparatus. The inner case is designed to also function as ashield case for the electronics. The electronic apparatus may be a videoprojector, in which case the intake openings are preferably providednear a rear end surface of the video projector.

With the arrangements that the inner and outer case together constitutea dual housing structure for the electronic apparatus and the intakechamber is defined in the area where the intake openings of the casesare provided, external air to be introduced into the electronicapparatus is temporarily stored in the intake chamber and then directedto the interior of the apparatus. Because the inventive arrangements canthus provide a wider air flow passage, air intake noise and noise causedby a motor/fan unit disposed in the interior can be effectivelyprevented from greatly leaking out of the electronic apparatus. Further,because the intake opening of the inner case and the intake opening ofthe outer case in the invention are displaced from each other withrespect to the front-and-rear direction of the electronic apparatus(namely, the intake openings of the inner and outer cases are not inlinear alignment along the front-and-rear direction of the electronicapparatus) so as to provide a nonlinear intake passage, the noise causedby the interior motor/fan unit can be prevented even more effectivelyfrom leaking out of the apparatus. Furthermore, with the inner casedesigned to also function as the shield case, leakage, from theelectronic apparatus, of electromagnetic noise can also be prevented.

Generally, in many home theaters, people view the screen while sittingor standing behind the video projector; thus, in the present invention,the intake openings are provided near the rear end surface of the videoprojector with exhaust openings provided to open outwardly from a frontend surface of the electronic apparatus, with a view to avoiding theexhaust air from blowing against the viewers behind the projector.

According to another aspect of the present invention, there is provideda video projector, which comprises: a projecting lens provided in afront end section of the video projector; a fan provided on one of leftand right sides in the front end section for discharging exhaust airfrom within the video projector; a silencer provided on other of theleft and right sides in the front end section, for silencing the exhaustair discharged via the fan; and a duct connecting between the fan andthe silencer while bypassing an underside or upside of the projectinglens.

Preferably, in the portion of the duct which bypasses the projectinglens, the duct has a reduced height but an increased dimension in thefront-end-direction of the video projector (i.e., width or depth) tomake up for the reduced height in such a manner that the duct has asubstantially uniform sectional area throughout its length. The duct maycomprise a cover constituting a front portion thereof and a bodyconstituting a rear portion thereof. Preferably, the body of the ducthas a substantially flat rear surface and the cover has a width in thefront-and-rear direction varying in corresponding relation to avariation in height of the cover so that the cover has a curved frontsurface. The silencer may have an intake port formed in a side surfacethereof and an exhaust port formed in a front surface thereof, and thesilencer may have an inner wall surface made of a sound absorbingmaterial. The video projector may further comprise an inner case thathouses a lamp and electronic circuitry and an outer case disposedoutside the inner case. In this instance, the fan is connected to theinner case, and the fan, duct and silencer are each disposed between theinner case and the outer case.

With the arrangement that the fan and silencer are disposed to the leftand right of the projecting lens and interconnected via the duct, thepresent invention can increase the overall length of the duct, i.e. anexhaust discharge section, and thus can reduce the noise caused by thedischarge of the exhaust air. Further, because the duct bypasses theunderside or upside of the projecting lens, namely, because the fan,silencer and duct are installed using the area where the lens isprovided, it is possible to install these fan, silencer and duct withouthaving to increase the dimension, in the front-and-rear direction, ofthe video projector.

Further, because the duct bypasses the underside or upside of theprojecting lens, namely, because the fan, silencer and duct areinstalled using the area where the lens is provided, it is possible toinstall the fan, silencer and duct without having to increase thedimension, in the front-and-rear direction, of the video projector.

In the portion bypassing the projecting lens, the duct has a reducedheight, but it has an increased width or depth to make up for thereduced height in such a manner that the duct has a substantiallyuniform sectional area throughout its length. This arrangement can avoidan increase in resistance to the air despite the variation in thesectional shape of the duct, and thus can prevent degradation of theexhaust discharge efficiency. Further, because the width variation ofthe duct is achieved by varying the shape of the duct's front surface,the rear surface of the duct can be made practically flat, so that theduct can be installed with ease.

Further, in the video projector of the present invention, the silencertakes in air via the intake port provided in its side surface anddischarges the air via the exhaust port provided in its front surface.Namely, the silencer discharges the air after causing the air to impingeagainst the shock absorbing surface and deflect by 90 degrees, with theresult that the exhaust discharge sound can be subdued even moreeffectively. Furthermore, because the lamp and electronic circuitry arehoused in the inner case, the exhaust discharge section only has todischarge the air out of the inner case. Thus, the fan, duct andsilencer can be installed outside the inner case, i.e. snugly betweenthe outer case and the inner case, and thus the video projector can havean improved outer appearance.

According to still another aspect of the present invention, there isprovided a structure for mounting a fan unit to a fan case, whichcomprises: gel-state shock absorbers; and at least three mountingportions formed on front and rear surfaces of the fan unit. Here, the atleast three mounting portions are attached to the fan case via thegel-state shock absorbers. The mounting portions of the fan unit maycomprise two pairs of front and rear mounting portions formed, inopposed relation to each other, on the front and rear surfaces of thefan unit, in which case the two pairs may be spaced apart from eachother on an imaginary straight line passing a rotation shaft of a fan ofthe fan unit or the center of gravity of the fan unit.

In this invention, the fan unit is supported by being sandwiched at itsfront and rear surfaces, rather than at its corners. The gel-state shockabsorbers are used as means for supporting the fan unit relative to thefan case. Because the gel-state shock absorbers have good thermalcharacteristics and extremely high vibration absorbing characteristics,vibrations of the fan unit can be prevented from being transmitted tothe fan case, even in a situation where the fan discharges hot exhaustair and the gel-state shock absorbers are exposed to the hot dischargeair. Further, because the fan unit is supported by being sandwiched atits front and rear surfaces, horizontal vibrations of the fan unit(e.g., those caused by an offset in the center of gravity of the fan)can be absorbed by deformation, in shearing directions, of the gel-stateshock absorbers. As a result, the present invention can effectivelyavoid the problem that the vibrations of the fan unit are easilytransmitted to the fan case, as compared to the case where the fan unitis supported at its corners.

BRIEF DESCRIPTION OF THE DRAWINGS

For better understanding of the object and other features of the presentinvention, its preferred embodiments will be described hereinbelow ingreater detail with reference to the accompanying drawings, in which:

FIG. 1 is a plan view showing an inner structure of a video projector towhich is applied an embodiment of the present invention;

FIG. 2 is a front view of the video projector with its outer caseremoved;

FIGS. 3A and 3B are a plan view and a front view, respectively, of aduct employed in the video projector, which particularly show the ductwith a silencer attached thereto;

FIGS. 4A and 4B are a front view and a rear view, respectively, of amotor/fan unit received in the duct;

FIGS. 5A-5C are views showing an inner structure of a fan case portionof the duct; and

FIGS. 6A and 6B are views showing an inner structure of a silenceremployed in the video projector.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following will describe embodiments of the present invention, but itshould be appreciated that the present invention is not limited to thedescribed embodiments and various modifications of the invention arepossible without departing from the basic principles. The scope of thepresent invention is therefore to be determined solely by the appendedclaims.

FIG. 1 is a plan view showing an inner structure of a video projector towhich is applied an embodiment of the present invention, and FIG. 2 is afront view of the video projector with its outer case removed. The outercase 1 of the video projector is formed of resin, and an inner case 1designed to function as a shield case is made of aluminum 2 and disposedwithin the outer case 1. Further, within the aluminum-made inner case orshield case 2, there are provided an electronic circuit board 4, a lightsource lamp 5 and an image-reproducing optical unit 6. In the plan viewof FIG. 1, a front end surface of the video projector is depicted asfacing upward, and the image-reproducing optical unit 6 is provided on amiddle front end section within the shield case 2.

The image-reproducing optical unit 6 is positioned outwardly of thefront end of the shield case 2, i.e. between the shield case 2 and theouter case 1. Projecting lens 7 is disposed centrally in a front endsection of the video projector between the outer and inner cases 1 and2. The light source lamp 5 is disposed to the left of theimage-reproducing optical unit 6 as viewed from the front of the opticalunit 6 or video projector; hereinafter, the terms “left” and “right”refer to left and right sides as viewed from the front of the videoprojector. The light source lamp 5 is an incandescent lamp whichproduces a relatively great amount of light with power consumption inthe order of 150 watts. The image-reproducing optical unit 6 includes amirror, a color filter, a DMD (trademark) which stands for a digitalmicro-mirror device functioning as a light switching mirror device, andthe like. In the image-reproducing optical unit 6, the mirror directslamp light, having a color selected via the color filter, to the DMD.The color filter is rotated by an electric motor so as to supply thethree primary colors to the DMD on a time-divisional basis. The DMDcomprises a group of minute mirror elements of 1024×768 pixels.Reflecting directions of the individual mirror elements are varied byimage signals so that video images are reproduced by the individualmirrors. The video images reproduced on the DMD are projected via theprojecting lens onto a screen.

The electronic circuit board 4 includes an image processing circuitboard portion 4 a and an input-signal processing circuit board portion 4b. The image processing circuit board portion 4 a is disposed rearwardlyof the image-reproducing optical unit 6 and lamp 5, and the input-signalprocessing circuit board portion 4 b is disposed to the right of theshield case 2. Although not specifically shown, the video projector has,on its right side, input terminals for inputting various image signalsto the input-signal processing circuit board portion 4 b.

Two intake openings 1 a are provided in a rear end wall portion of theouter case 1 adjacent rear left and right corners of the case 1, and asingle exhaust opening 1 b is provided in a front end wall portion ofthe outer case 1 adjacent a front right corner of the case 1. Further, asingle intake opening 2 a is provided substantially in the middle of arear end wall portion of the shield case 2, and a single exhaust opening2 b is provided in a front end wall portion of the shield case 2adjacent a front left corner of the case 2. The exhaust opening 2 b ofthe shield case 2 is located immediately in front of the lamp 5 thatgenerates the greatest amount of heat.

In the rear end section of the video projector where the intake openings1 a and 2 a of the outer and inner cases 1 and 2 are provided, the outercase 1 and shield case 2 are spaced from each other by a sufficientdistance such that an intake chamber 3 is defined between the rear endwall portions of the outer case 1 and shield case 2. The defined intakechamber 3 has a capacity which is larger than the balance of an air flowwhich is introduced from the intake openings 1 a of the outer case 1 andan air flow which is taken from the intake openings 2 a of the shieldcase 2. Therefore, velocity of flow in the intake chamber 3 is reducedand air stays in the intake chamber 3 to prevent direct flow from theintake openings 1 a to the intake openings 2 a. With the intake openings1 a provided at left and right locations with respect to the center inthe rear end wall portion of the outer case 1 and the single intakeopening 2 a provided centrally in the rear end wall portion of theshield case 2, the intake openings 1 a of the outer case 1 and theintake opening 2 a of the shield case 2 are displaced from each otherwith respect to the front-and-rear direction of the video projector(i.e. out of linear alignment with each other along the front-and-reardirection) and are laterally offset from each other (left-and-rightdirection in the paper sheet) so as not to be acoustically connectedwith each other, so that noisy sounds caused by ventilation (ventilatingsounds) within the outer case 1 can be effectively prevented fromleaking through the backside of the video projector to the outside. Theventilating sounds include operating sounds of the electric fan, motorrotating the color filter and whizes caused by air flowing among variouscomponents within the video projector. Filter 11, which is in the formof a sponge or open-cell foam, is provided in each of the two intakeopenings 1 a of the outer case 1.

As described, the video projector of the present invention ischaracterized in that it includes a dual housing structure composed ofthe outer case 1 and inner or shield case 2, the outer case 1 and shieldcase 2 are spaced apart from each other to define the intake chamber 3and the intake openings 1 a of the outer case 1 and the intake opening 2a of the shield case 2 are aligned in an offset manner with each otherin the front-and-rear direction. Such characteristic arrangements cangreatly contribute to reduction of the noisy sounds caused by theventilation operations in the video projector. Specifically, with thearrangements, it is possible to reduce the noise leaking out through theintake openings by 2 dB.

In the front end section of the video projector, a motor/fan unit 8 fordischarging exhaust air, duct 9 and silencer 10 are provided between theshield case 2 and the outer case 1. The motor/fan unit 8 is housed in afan case portion 9 a of the duct 9 and opposed to the exhaust opening 2b of the shield case 2. The motor/fan unit 8 includes a so-calledsirocco fan 83 (see FIG. 4) that takes in external air through a sidesurface portion thereof and discharges the air in circumferentialdirections. More specifically, the motor/fan unit 8 takes in the airfrom within the shield case 2 and then discharges the taken-in air intoa body portion 9 b of the duct 9. Thus, the heat generated by the lamp 5can be discharged via the duct 9 to the outside without flowing in theshield case 2. The duct body portion 9 b is located in the front endsection of the video projector between the outer case 1 and the shieldcase 2, and it interconnects the fan case portion 9 a disposed on theleft of the projector's front end section and the silencer 10 disposedon the right while bypassing the underside of the projecting lens 7.With the duct body portion 9 b bypassing the projecting lens 7, the lens7 is provided centrally in the front end section of the video projectorand thus can be operated with increased ease. Further, because the duct9 interconnecting the fan case portion 9 a and silencer 10 disposed tothe left and right of the lens 7 has an increased length, there can beattained an enhanced sound reducing effect. The silencer 10 causes theair flowing from the duct 9 to impinge against its sound absorbing innersurface and then discharges the air via its exhaust port, as will belater described. The exhaust opening 1 b of the outer case 1 is in theform of a grille.

Also, a small fan 12 is provided for the input-signal processing circuitboard portion 4 b, and this fan 12 and the silencer 10 are connected influid communication with each other via a small exhaust hole 2 c formedin the shield case 2.

FIGS. 3A and 3B are a plan view and a front view, respectively, of theduct 9, which particularly show the duct 9 with the silencer 10 attachedthereto. As shown, the duct 9 includes the fan case portion 9 a and bodyportion 9 b. The fan case portion 9 a houses the motor/fan unit 8provided with the sirocco fan and has an opening formed in a backsidethereof adjacent the shield case 2. The duct 9 takes in the air fromwithin the shield case 2 via the backside opening, and directs thetaken-in air to the body portion 9 b The body portion 9 b interconnectsthe fan case portion 9 a and silencer 10 while bypassing the undersideof the projecting lens 7. In the portion of the duct body portion 9 bwhich bypasses the projecting lens 7, the body portion 9 b has a reducedheight but an increased depth (dimension in the front-and-rear directionof the video projector) to make up for the reduced height, in such amanner that the body portion 9 b has a substantially uniform sectionalarea throughout its length.

In the plan view of FIG. 3A, the duct 9 is shown as composed of a body20 constituting a rear surface of the duct 9 and a cover 21 constitutinga front surface of the duct 9. The rear surface of the body 20 is madeup of three flat surfaces, the middle one of which lies flush with therear surface of the fan case section 9 a. This flat rear surface featureallows the duct 9 to be easily attached to the shield case 2. The cover21 of the duct 9 bulges rearwardly to have a greater width in and arounda center thereof, so as to make up for the reduced height. The depth orwidth (dimension in the front-and-rear direction of the video projector)of the cover 21 increases according as the height of the duct 9decreases. Thus, when the body 20 and cover 21 are assembled together,the duct body portion 9 b has a substantially uniform sectional areathroughout its length. Because the sectional area does not vary despitea variation in the sectional shape of the duct body portion 9 b, the airdischarged from the duct 9 presents no variation in pressure and hencedoes not exhibit great resistance to fluid. Further, most of thevariation in width of the duct 9 is provided by curving the surface ofthe cover 21, the rear surface of the body 20 can be made flat, whichfacilitates attachment of the duct 9 to the shield case 2.

FIGS. 4A and 4B are a front view and a rear view, respectively, of themotor/fan unit 8. The motor/fan unit 8 is mounted within the fan caseportion 9 a in such an orientation where the front surface of FIG. 4Afaces the exhaust opening 2 b of the shield case 2. This motor/fan unit8 includes the sirocco fan 83 driven by an electric motor (not shown)and a casing 80 shaped like a spiral shell. The casing 80 has a circularintake port 84 in its front wall portion and an exhaust port 85 in itsside wall portion. The sirocco fan 83 is provided to turn along thecircumference of the intake port 84. The casing 80 also has two pairs offront and rear mounting portions 81 each in the form of a radialprojection, and each of the mounting portions 81 has a screw hole 82.Specifically, the pairs are angularly spaced apart from each other, andin each of the pairs, the front and rear mounting portions 81 arealigned with (opposed to) each other in the front and-rear direction ofthe video projector; that is, the pairs are spaced apart from each otheron an imaginary straight line passing the rotation shaft of the fan ofthe fan unit or the center of gravity of the fan unit. The twoangularly-spaced-apart front mounting portions 81 are provided on thefront surface of the casing 80, while the two angularly-spaced-apartrear mounting portions 81 are provided on the rear surface of the casing80. The two mounting portions 81 are symmetrical to each other withrespect to the rotation shaft 83 c of the sirocco fan 83, and thesemounting portions 81 function to prevent undesired vibrations of thesirocco fan 83 during the rotation.

Note that the motor/fan unit 8 in this video projector is fixed to thefan case 9 a via a gel-state shock absorber 19 (FIG. 5) affixed to theouter surface of each of the mounting portions across the screw hole 82,rather than via a screw threaded through each of the screw holes 82. Thegel-state shock absorbers may each be Solbosein (trademark) or the like.

FIGS. 5A-5C show the interior of the fan case portion 9 a in the body 20of the duct 9. The fan case portion 9 a has an opening 93 formed in itswall surface in alignment with the intake port 84 formed in the casing80 of the motor/fan unit 8. Ring-shaped rib 91 is formed along theperiphery of the opening 93 to fill a gap between the fan unit 8 and thefan case portion 9 a. Note that this rib 91 is positioned out of contactwith the casing 80 of the motor/fan unit 8. Further, a rectangular rib92 is formed around the opening 93, which fits into the exhaust opening2 b of the shield case 2. The exhaust port 85 of the motor/fan unit 8received in the fan case portion 9 a is positioned in alignment with aconnection 94 between the fan case portion 9 a and the duct body portion9 b. In the connection 94, the motor/fan unit 8 and fan case portion 9 aare in close proximity to (but not in contact with) each other and theduct body portion 9 b has the same inside dimensions as the exhaust port85 of the motor/fan unit 8, so that the exhaust of the motor/fan unit 8can be discharged to the duct body portion 9 b with almost no leakage.

As shown in a sectional view of FIG. 5B, the motor/fan unit 8 issupported via the gel-state shock absorbers 19 affixed between themounting portions 82 of the unit 8 and supporting regions of the fancase portion 9 a. The motor/fan unit 8 does not contact the fan caseportion 9 a even in its regions where the intake port 84 and exhaustport 85 are formed. Thus, vibrations of the motor/fan unit 8 due to therotation of the fan can be effectively absorbed by the gel-state shockabsorbers 19 and hence can be prevented from being transmitted to theduct 9 and shield case 2. As a consequence, noisy sounds produced by theventilating fan can be reduced to a significant degree.

Because the gel-state shock absorbers 19 are adhesive by themselves,they can be sufficiently affixed to the mounting portions 81 of themotor/fan unit 8 (casing 80) and the fan case portion 9 a by just beingpressed against the mounting portions 81 and the inner surface of thefan case portion 9 a, and horizontal vibrations of the motor/fan unit 8can be absorbed by deformation, in shearing directions, of the gel-stateshock absorbers 19.

As shown in FIG. 5C, each of the supporting regions of the fan caseportion 9 a is preferably in the form of a recess 90. In this case, theinner surface of each of the disk-shaped gel-state shock absorbers 19has a central region bulging inwardly to fit into the screw hole 82 ofthe corresponding mounting portion 81, and the outer surface of each ofthe disk-shaped gel-state shock absorbers 19 fits into the correspondingrecess 90 of the fan case portion 9 a. This arrangement can prevent thehorizontal vibrations of the motor/fan unit 8 even more effectively.

FIGS. 6A and 6B show an inner structure of the silencer 10. FIG. 6A is afront view of the silencer 10 with a silencer cover removed to show theinterior of the silencer 10. The interior of the silencer 10 is dividedinto two chambers, upper silencing chamber 72 and lower silencingchamber 73. The upper silencing chamber 72 has an intake port 74, viawhich the chamber 72 is connected to the duct 9. The lower silencingchamber 73 has an intake port 75, via which the chamber 73 is connectedto the small exhaust hole 2 c that is provided for the input-signalprocessing circuit board portion 4 b. As seen from FIGS. 2 and 3,exhaust ports 70 and 71 of the upper silencing chamber 72 and lowersilencing chamber 73 are formed in the cover of the silencer 10. Theinner surface of the silencer 10 is covered with a sound absorbingmaterial 76 such as urethane sponge. The intake port 74 and exhaust port70 of the upper silencing chamber 72 are interconnected by a passagebent 90 degrees, so that the air flowing in from the duct 9 impingesagainst the absorbing material 76 on the inner surface of the chamber 72to be deflected toward the exhaust port 70 and is then discharged viathe exhaust port 70. Further, the intake port 75 and exhaust port 71 ofthe lower silencing chamber 73 are interconnected by a passage bent intoa crank-like shape, so that the air flowing in from the duct 9 impingesagainst the absorbing material 76 of the chamber 73 to be deflectedtwice toward the exhaust port 71 and is then discharged via the exhaustport 71. Because the exhaust air from the duct 9 is discharged afterimpinging against the absorbing material 76 and being deflected by theimpingement as set forth above, noise caused by the ventilating fan andother ventilation operations can be significantly lessened.

Whereas the image-reproducing optical unit 6 in the embodiment has beendescribed as employing the DMD (digital micro-mirror device), the DMDmay be replaced with another suitable device such as a liquid crystaldisplay (LCD) device.

Further, whereas the embodiment has been described as applied to thevideo projector, the ventilating mechanism and silencing mechanismdisclosed herein may be applied to any other electronic apparatus, suchas a printer and a personal computer.

Further, the duct 9 may be positioned in such a manner that the ductbody portion 9 a bypasses the upside, rather than the underside, of theprojecting lens 7.

Furthermore, in the above-described embodiment, two pairs of the frontand rear mounting portions 81 are provided on the front and rearsurfaces of the motor/fan unit 8—two angularly-spaced-apart mountingportions 81 on each of the surfaces—utilizing the screw holes of theunit 8. However, the present invention is not so limited; for example,the motor/fan unit 8 may have three such front and rear mountingportions 81 that are angularly spaced apart from each other so that themotor/fan unit 8 can be supported with increased stability. In such acase, the motor/fan unit 8 may be supported by at least two mountingportions 81 provided on one of the surfaces (front or rear surface) andone mounting portions 81 provided on the other surface (rear or frontsurface).

In summary, the present invention is characterized by the dual housingstructure composed of the outer and shield (inner) cases and theprovision of the intake chamber between the outer and inner or shieldcases. With such arrangements, the present invention can minimize noiseleaking out of the apparatus to the outside while performing asufficient cooling function.

Further, with the arrangement that the fan and silencer are disposed tothe left and right of the projecting lens and interconnected via theduct in the front end section of the electronic apparatus, the presentinvention can increase the length of the exhaust discharge section andthus reduce the noise caused by the fan. Because the duct bypasses theunderside or upside of the projecting lens, it is possible to avoid anincrease in overall size of the electronic apparatus. Further, with thearrangement that the fan unit is supported at its front and rearsurfaces by the gel-state shock absorbers, the present invention canprevent the vibrations caused by the rotation of the fan from beingtransmitted to the fan case to cause noise.

1. A ventilating structure for an electronic apparatus comprising: aninner case that houses electronics; and an outer case that houses saidinner case, said inner case and said outer case each having an intakeopening, said inner case and said outer case being spaced from eachother, in an area where the intake openings are provided, by asufficient distance such that an intake chamber is defined between saidinner case and said outer case and air stays in said intake chamber toprevent direct flow from the intake opening of said outer case to theintake opening of said inner case.
 2. A ventilating structure as claimedin claim 1 wherein the intake opening of said inner case and the intakeopening of said outer case are displaced from each other with respectiveto a front-and-rear direction of said electronic apparatus so as toprovide a nonlinear intake passage.
 3. A ventilating structure asclaimed in claim 1 wherein said inner case functions also as a shieldcase.
 4. A ventilating structure as claimed in claim 1 wherein saidelectronic apparatus is a video projector, and the intake openings areprovided near a rear end surface of said electronic apparatus.
 5. Avideo projector comprising: a projecting lens provided in a front endsection of said video projector; a fan provided on one of left and rightsides in the front end section for discharging exhaust air from withinsaid video projector; a silencer provided on other of the left and rightsides in the front end section, for silencing the exhaust air dischargedvia said fan; and a duct connecting between said fan and said silencerwhile bypassing an underside or upside of said projecting lens.
 6. Avideo projector as claimed in claim 5 wherein in a portion of said ductwhich bypasses said projecting lens, said duct has a reduced height butan increased width in a front-and-rear direction of said videoprojector, to make up for the reduced height in such a manner that saidduct has a substantially uniform sectional area throughout a lengththereof.
 7. A video projector as claimed in claim 6 wherein said ductcomprises a cover constituting a front portion thereof and a bodyconstituting a rear portion thereof, and wherein said body of said ducthas a substantially flat rear surface and said cover has a width in thefront-and-rear direction varying in corresponding relation to avariation in height of said cover so that said cover has a curved frontsurface.
 8. A video projector as claimed in claim 5 wherein saidsilencer has an intake port in a side surface thereof and an exhaustport in a front surface thereof, and wherein said silencer has an innerwall surface made of a sound absorbing material.
 9. A video projector asclaimed in claim 5 which further comprises an inner case that houses alamp and electric circuitry and an outer case disposed outside saidinner case, and wherein said fan is connected to said inner case, andsaid fan, said duct and said silencer are disposed between said innercase and said outer case.